This invention relates to a hook latch and more particularly, to an adjustable, flush mounted, over-center hook latch of the type used to secure aircraft panels.
Over-center hook latches are well known in the art. One such latch is shown in U.S. Pat. No. 2,712,955. As seen in this patent, the fulcrum axis of latch handle is mounted to a bracket on the aircraft panel and the latch hook engages a keeper on the aircraft structure. The latch is referred to as an over-center latch as when the latch is closed, the load on the latch hook creates a moment arm on the latch handle about the fulcrum axis in a direction which maintains the latch handle in its closed position.
The distance between the latch hook and the keeper is critical and must be maintained. If the distance is too great, the latch either will not close or will create excessive compression forces on the aircraft components and thereby possibly damaging them or the latch. If the distance is too close, the hook will not engage the keeper with suitable tension to maintain the panel on the aircraft. Consequently, it has been known to provide some type of adjusting means either in the latch itself or on the keeper to accurately adjust the hook relative to the keeper during initial installation and subsequently when stresses in the aircraft may misalign the aircraft components.
A disadvantage of prior adjusting means is that the latch must be open to make the adjustment. Since the proper distance of the hook and resulting tension on the latch cannot be ascertained until the latch is closed, it is therefore often necessary through trial and error to make several adjustments by opening and closing the latch before final correct adjustment is obtained. This is even more critical when a plurality of latches are aligned in a row on a large aircraft panel. Here, it has been found that after adjusting the latch, adjustment of the next latch may adversely effect the adjustment of the prior latch such that the whole process has to be repeated. The opening and closing of the latch to effect the adjustment is both time-consuming and combersome.
Another disadvantage of prior latches is that the tension in the latch is measured by the tension on the handle at or near its closed position. Consequently, the handle must be opened and pulled outwardly by a tension measuring device to determine the tension in the latch. The measurement is often inaccurate and difficult.